Mineral oil composition



PatentedJune 13, 1939 PATENT OFFICE MINERAL OIL COMPOSITION Robert C.Moran, Wenonah, William H. James, Paulsboro, and Everett W. Fuller,Woodbury, N. J., assignors to Socony-Vacnnm Oil Company, Incorporated,New York, N. Y., a corporation of New York No Drawing.

Application March 5, 1938,

Serial No. 194,076

4 Claims.

This invention has to do in a general way with the production of mineraloil compositions and is more particularly related to the production ofmineral oil compositions having characterizing properties which renderthem especially suitable for use as lubricants for turbines and asdielectrics" for electrical equipment such as trans form substantialquantities of insoluble sludge.-

Such sludge formation clogs the pipes and vents in the oil circulationsystem of a turbine and the cooling ducts of a transformer. By formingfilms on the insulation it reduces the heat transfer in' electricaltransformers and in addition it substantially reduces the dielectricproperties of the This tendency to form sludge may be reduced bytreating the oils withvery large amounts of sulfuric acid or ofselective solvents, but such highly refined oils are expensiveto preparebecause of high treating losses and the large quantities of refiningagents used. Furthermore, the very highly refined oils tend to formacidic products which attack metals with which, they come in contact andalso lower the dielectric properties of the oil.

The cost and other disadvantages of these highly refined oils have ledto the investigation of means whereby oil fractions moderately" refinedto meet turbine and transformer specifications might be treated by theaddition of an agent which would act as a negative catalyst to retardorinhibit the formation of sludge, under these con- ,ditions of use.These investigations, which have been relatively extensive in scope,have led to the suggestion of a number of materials as inhibitors ofsludge formation in moderately refined oils such,; for example, asphenyl alpha naphthylamine and various organic salts of heavy metals.These materials, however, are not entirely satisfactory because oftheir, low inhibiting effect, their cost, etc.

The present invention has as its primary object the production of anon-sludging moderately refined mineral oil for use in turbines andtransformers and is predicated upon the discovery,

after extensive investigation and experimentation, of a compound whichpossesses outstanding characteristics as an inhibitor or negativecatalyst toward sludge formation in moderately refined mineral oilfractions that normally tend to form sludge under the conditions of useencountered in turbines and transformers.

It is a further object of this invention to provide a method ofinhibiting sludge formation in moderately refined mineral oil fractionsunder the conditions of use encountered in turbines and transformers.

This invention, which is a continuation in part m of the copendingapplication of Robert C. Moran andwilliam H. James, two of the inventorsnamed herein, Serial Number 146,595, filed June 5, 1937, is based uponthe discovery that aniline disuif-lde (diamino diphenyi disulflde), whenadmixed in i6 minute'quantities with moderately refined, normallyvsludging oils, produces outstanding reductions in the rate of sludgeformation and renders such oils more suitable for use in turbines andtransformers.

By the term aniline disulflde as used herein to identify the compoundsor materials characterizing the improved'non-sludging turbine oils andtransformer oils contemplated by this invention, we have reference tothe product obtained by reacting aniline with elementary sulfur atelevated temperature. (Hodgson, J. Chem. Soc. 125, 1855 (1924).)

For example, two molesof aniline and three atoms of sulfur are mixedtogether and heated to a temperature of about to C. In the reactionwhich takes place aniline disulilde (d iamino diphenyl disulfide) isformed with the evolution of hydrogen sulfide gas according to thefollowing equation:

35 Z :2+3S)OSS Q+H2S I NH: H: NH: 7 The first aniline disuliide productformed in 40 the above reaction is 2,2 diamino diphenyl dissulflde, but4,4 diamino diphenyl disulilde is formed in increasing'proportions asthe temperature rises. There is also some formation of the 3,3 diaminodiphenyl disulfide. 45

The unreacted aniline is removed from the reaction mixture by steamdistillation. The product is freed from unreacted sulfur by convertingthe aniline disulfldes to their hydrochlorides and extracting with hotwater. The hydrochloride 50 salt extract is then neutralized with a basesuch as sodium hydroxide to obtain an aniline disulflde product whichhas been satisfactorily used in the practice of thisinvention.

The product obtained by the above procedure 55 ature the isomer 2,2diamino diphenyl disulfide melts at 03 0., the 3,3 isomer melts at 50-80C. andthe4.4'isomermeltsat81 to82C. Itwillthereforebeapborenttothoseiamiliar withthe ariatlia'tthisproductisamixtureofisomericv aniline disulfides This mixtureof isomers has proved satisfactory for the purposesof inhibiting smudgeformation in normally sludgin'g turbine oils and the like, and the termaniline di sulfide as used herein is intended to include such anisomeric nlxtu're as well as the individual isomers of which it iscomprised.

The following examples illustrate the effectiveness of aniline disulfideas an inhibitor of sludgeformation in mineral oils of the normally sludgat 100 1''. and a flash point of 280 F. The physical characteristics ofthe oil were of the type suited for transformer use. When 'a sample ofthis oil alone was heated for seven days at 120 C. in the presence of apiece of copper foil with ongen gas bubbling therethrough at the rate of2000 cc. per hour, a very heavy precipitate of sludge had formed in theoil. A similar sample of this same oil containing 05% by weight ofaniline disulfide treated inthe same way formed relatively littleprecipitate.

Emmple B To demonstrate the value ofaniline disulfide as a sludgeinhibitor in oils of the type used in turbines several turbine-type oilswere subjected to the following test procedure: A 25 cc. sample of oilwas heated to 200 F. with five liters of air per hour bubblingtherethrough. During this treatment twenty-four inches of eighteen gaugearoaaos melts at about w-ssc. According to the u -if copper wire and onegram of iron granules were maintained in the sample and 2 cc. ofdistilled water were added each day. The tests were conducted with thesamples of oil alone and with the samples of oil containing anilinedisulfide and were conducted over varying periods of time. The sludgeformed was measured at the end of these varying'time intervals bycentrifuging the oil, washing the precipitate thrown out with petroleumether and weighing such precipitate.

In the tables given below we have set out briefiy the specifications ofthe oil samples used at the head of each table and have tabulated thetime in hours at the end of which the sludge precipitate was measuredfor the oil alone and the oil plus .10% of aniline disulfide. The amountof sludge formed. as set out in the tables below, is expressed inmilligrams of sludge formed in 25 cc. of oil during the time intervalset out in the first column.

Tablev I Oil used-A mineral oil fraction refined by the Duo-Sol methodto give a product with A. P. I. gravity of 31.1, Saybolt viscosity of158 seconds at 100 F. and flash point of 410 F.

Table 11 Oil ME'PA mineral oil fraction refined with furfural to atwenty-five per cent loss: A. P. I. gravity of 31.8 and Bayboltviscosity of 138 seconds at 100' I".

Oil used-A mineral oil fraction refined with furfural to an A. P. I.gravity of 27.6, Saybolt viscosity of 260 seconds at 100 1''.

m Sludge on alone m 24 Do I ass as Ol|+.l0% aniline disulfide m 21 Do-.1,412. as

Table 1v? Oil used.A mineral oil fraction refined with Chlorex to an A.P. I. gravity of 33.1 and Saybolt viscosity of 135 seconds at 100 1''.

Sludge 011m... s4 11 Do m 103 Do m 253 0n+.1o% inhibitor ms 12 Do s00 4a572 69 From the foregoing tabulated-results it will be apparent thatthrough the uso' of aniline disulfide as a sludge inhibitor we are able.to'obtain from a moderately refined mineral oil 'fra'ction, potentiallysusceptible to the formation of sludge under the conditions of usenormally encountered in a turbine. an oil compositionwhich issubstantially inhibited against such sludgeformation. In addition to theforegoing laboratory tests turbine oils of the above type are beingsubjected to use with outstanding success in actual turbine operation,which further demonstrates. the effectiveness of aniline disulfide as asludge inhibitor; 7

We claim:

1. A mineral oil composition of the type adapted for use in turbines andtransformers comprising a moderately refined mineral oil potentiallysusceptible to the formation of sludge under the conditions of usenormally encountered in turbines and transformers and a minor proportionof aniline disulfide, suincient to resist the formation of said sludgeunder said conditions of use.

2. A mineral oil composition comprising a mineral oil moderately refinedto meet specifications for turbine use and potentially susceptible tothe formation of sludge under the conditions of use encountered in aturbine and a minor proportion of aniline disulfide, sumcient to inhibitthe formation of sludge under said conditions of use.

3. A mineral oil composition of the type adapted for use in turbines andtransformers comprisinga' moderately refined mineral oil potentiallysusceptible to the formation of sluge under the conditions of usenormally encountered in turbines and transformers and a minor proportionof a mixture of isomeric aniline disulfides, sufiioient to resist theformation of said sludge under said conditions of use.

4. A lubricant composition comprising a mineral oil moderately refinedto meet specifications for transformer use and potentially susceptibleto the formation of sludge'under the conditions of use encountered in atransformer and minor proportion of aniline disulflde, suflicient toinhibit the formation of sludge under said conditions of use.

